“I’ve made it very clear that I don’t want Donald Trump to be the next president of the United States,”
Mr. Romney also holds Mr. Trump’s running mate, Senator JD Vance of Ohio, in particularly low esteem.
“I don’t know that I can disrespect someone more,” Mr. Romney told his biographer, McKay Coppins of The Atlantic, last year.

This is not too far off from Uncommitted’s non-endorsement of Harris - won’t explicitly endorse her but asks to make sure the other guy doesn’t become President.